Rattle/squeak from oil pan/ exhaust area? 95 chevy

My 95 2500 350 started to make a strange, fairly loud sound today after I changed the spark plugs, wires, cap, and rotor. I also changed the oil and filter. The sound seems to be coming from underneath the motor around the exhaust or possibly the oil pan area. I tried putting a large piece of metal up to my ear and touching it to various parts of the motor, including the oil pan, but I could not locate the source of the sound. I would describe the sound as a squeak, or a rattle. It almost sounds like something is rattling around inside the exhaust. The sound increases with the rpm's, and seems to go away in the middle to higher rpm. Once the truck has warmed up completely, the sound goes away. I have noticed this same sound on a couple of occasions in the past, but only for a couple seconds.

I disconnected each spark plug one by one with no luck. I will try a compression test tomorrow. Any ideas?

I used 5-30 as opposed to the normal 10-w30 that I usually use. (they were out of the 10w30) . The truck has about 150,000 miles on it. I actually mixed up 2 wires originally, but I noticed that right away. I will re-check the firing order, but the truck seems to drive fine, and the noise goes away when its warmed up. Oil pressure seems fine (according to the stock gauge).

Wow dude thats kinda weird, should have lots of miles left on that engine. Maybe drain the oil and replace it with 10/40. 5/30 is kinda light for a big truck engine that is being worked hard.

Come to think of it, my Honda does the same thing in the morning. on first start of the day. Like this quite, higher pitched (not like a rod knock) like more of a ping but with some rattle in it. If that makes any sense.

I believe it is the valves need adjusted, but it does have 342.000 miles on the original engine...........And i dont really have time or ambition to fix it. Now that i think of it, i don't care either, been doing it a long time.

Wow dude thats kinda weird, should have lots of miles left on that engine. Maybe drain the oil and replace it with 10/40. 5/30 is kinda light for a big truck engine that is being worked hard.

Click to expand...

Yeah I was hoping to get at least 200k out of it. Someone on another site told me that his truck did the same thing and it turned out to be a cracked flexplate... The noise does sound like its coming from underneath the car, and before I read his post I listened to the bellhousing with the extension up to my ear because it sort of sounded like that might be the culprit. I did not hear anything though.

Its not the catalayic converter because I don't have on on the truck. I'm familier with the cat-rattle (my other truck does it) and its louder than that.

Sheet metal jackets on the exhaust manifolds can easily be shaken loose, especially when you mentioned changing spark plugs. Exhaust manifolds on that model year are also notorious for cracking just about the flange.

Sheet metal jackets on the exhaust manifolds can easily be shaken loose, especially when you mentioned changing spark plugs. Exhaust manifolds on that model year are also notorious for cracking just about the flange.Plan on a $360.00 part cost if that is the problem.

Click to expand...

I'll check that out, but I'm not sure why it would make the noise when its warming up....if the manifold turns out to be the problem, i'll pick up a pair of headers for that price...